Two-way roller clutch assembly

ABSTRACT

A driveline assembly includes first and second axle half-shafts having first and second side gears mounted thereon, an axle housing, a differential case rotatably mounted within the axle housing, a least two spider gears rotatably mounted within the differential case, and a clutch assembly coupled to the differential housing and one of the axle half-shafts and including an outer race having a cylindrical inner surface and an inner race having a cammed outer surface coaxial with the cylindrical inner surface and defining a gap therebetween and a roller clutch disposed within the gap; a biasing element to bias the roller clutch to a disengaged position; and an actuator to selectively overcome the biasing element to engage the roller clutch and lock the outer race and inner race and prevent relative rotation between the outer race and inner race.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application from U.S. patentapplication Ser. No. 09/908,402, filed Jul. 18, 2001 which claims thebenefit of related provisional application Serial No. 60/223,882 filedAug. 8, 2000.

TECHNICAL FIELD OF THE INVENTION

[0002] This invention is related to a vehicle drive line havingdifferential equipped with a two way over-running clutch. Morespecifically, the present invention relates to a vehicle drive linehaving a differential equipped with a two-way over-running clutchassembly of a roller/ramp variety which can be controlled forselectively locking up an automotive differential assembly.

BACKGROUND OF THE INVENTION

[0003] This invention is related to devices and methods as described inU.S. Provisional Application No.: 60/223,882, filed Aug. 8, 2000, andU.S. Provisional Application No.: 60/258,383, filed Dec. 27, 2000, allof which are commonly assigned.

[0004] Differential assemblies are used in motor vehicles to allow thewheels to turn at different rotational speeds while still providingpower to the wheels. Various types of differential assemblies are usedin motor vehicles to redirect the transfer of power to the drivingaxles.

[0005] In a standard differential, as a vehicle turns, power continuesto be provided through pinion and ring gears to the differentialhousing. As the inner and outer wheels describe different circles orradii, side gears attached to axle shafts are allowed to turn atdifferent speeds by the motion of intermediate spider gears. As longtraction is maintained between the drive wheels and the road service,the power is properly distributed to the wheels through the differentialassembly. However, when traction is reduced or lost altogether, astandard differential assembly will spin uselessly, providing littletractive power to the wheels. For instance, if one tire is on ice orsome other slippery service while the other is on dry pavement, slipwill occur at the low friction side and all the power through thedifferential assembly will be sent to the slipping tire. No power willbe delivered to the wheel on the dry pavement and the vehicle will notbe powered forward or backward. Therefore, there is a need to lock theaxle halves together in certain situations.

[0006] A differential assembly design that is used to overcome theshortcomings of the standard differential assembly is known as thelocking differential. A locking differential typically engages a “dog”clutch or an axial gear set to lock the two axle halves together.Unfortunately, locking differentials cannot be engaged “on-the-fly”because any relative motion between the gear teeth would result insevere mechanical damage. It would be desirable to selectively lock thedifferential assembly instantaneously during “on-the-fly” operation.

[0007] It is known in the art to selectively lock other drivetraincomponents using roller/ramp clutch assemblies. For example, the two-wayover-running clutch assembly described in U.S. Pat. No. 5,927,456,assigned to NTN Corporation, and hereby incorporated by reference,describes a clutch assembly of a roller ramp variety and the mechanismby which the rollers are retained and biased in the assembly. Inaddition, the rotation transmission device described in U.S. Pat. No.5,924,510, also assigned to NTN Corporation, and hereby incorporated byreference, discloses a device which includes a clutch assembly mountedin the transfer case of a four-wheel drive vehicle that can selectivelytransmit a driving force.

[0008] It would be desirable to provide this technology for use withdifferential assemblies to selectively lock the two axle halves togetherduring “on-the-fly” operation.

[0009] A primary object of this invention is therefore to provide atwo-way over-running clutch mechanism, such as that disclosed in U.S.Pat. No. 5,927,456 or U.S. Pat. No. 5,924,510, installed in thedifferential assembly of a motor vehicle which when energized will locktogether a side gear or drive axle and the differential housing so thatno relative rotation can occur between the two drive wheels. This systemwill provide on-demand traction and can be controlled by anelectromagnetic trigger clutch or by hydraulic, pneumatic or othermeans.

[0010] Another object of the present invention is to provide adifferential assembly which can be selectively locked togetherinstantaneously during “on-the-fly” operation.

BRIEF SUMMARY OF THE INVENTION

[0011] In accordance with an aspect of the present invention anover-running clutch assembly comprises an outer race having acylindrical inner surface and being rotatable about an axis and a caseend enclosing a first end of the outer race, an inner race having asegmented (flat or slightly concave) outer surface coaxial with thecylindrical inner surface and defining a gap therebetween. The innerrace is rotatable about the axis with rotational movement relative tothe outer race. A plurality of ramp surfaces formed at spaced apartlocations on the outer surface define a plurality of cammed surfaces onthe outer surface of the inner race. A plurality of rollers arepositioned between the outer race and the inner race with one of therollers being located centrally within each of the cammed surfaces andeach of the rollers having a diameter less than the gap between thecenter of the cammed surface on the inner race and the cylindrical innersurface of the outer race. A retainer interconnects all of the rollersand causes the rollers to circumferentially move in unison with oneanother. The retainer is rotatable about the axis with limited relativerotation with respect to the inner race. A first biasing element issupported on the retainer to radially bias the retainer positionrelative to the inner race such that each of the rollers is held in thecenter of the flat cammed surfaces on the inner race. An actuation diskis connected to the retainer by a means which allows some axial movementof the activation disk with respect to the retainer toward the case end.The preferred method would include a retainer tab extending axially fromone end of the retainer and a notch which is adapted to engage theretainer tab thereby preventing circumferential or relative rotationalmotion of the actuation disk relative to the retainer and allowing axialmotion of the actuation disk relative to the retainer. A second biasingelement is disposed between the actuation disk and the inner axialsurface of the case end to bias the actuation disk away from the caseend.

[0012] The clutch assembly includes an actuator to selectively overcomethe second biasing element to force the actuation disk into contact withthe case end, wherein rotation of the outer race and case end withrespect to said inner race is frictionally transferred to the actuationdisk and the retainer, overcoming the first biasing element, therebymoving the rollers along the ramp surfaces to a position where therollers engage and wedge between the inner and outer races to preventrelative rotation between the inner and outer races.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a partial sectional view of a portion of a vehicledriveline of the present invention;

[0014]FIG. 2 is a perspective view of an over-running clutch of thepresent invention;

[0015]FIG. 3 is a side sectional view of the over-running clutch of FIG.2;

[0016]FIG. 4 is a detail of a portion of the over-running clutch of FIG.3;

[0017]FIG. 5 is perspective view of the assembly of the inner race, theretainer, the rollers and the actuation disk for the over-runningclutch;

[0018]FIG. 6 is a sectional view of FIG. 5 taken along line 6-6;

[0019]FIG. 7 is a perspective view of a differential housing with anover-running clutch of the present invention; and

[0020]FIG. 8 is side sectional view of the differential housing of FIG.7.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The following description of the preferred embodiment of theinvention is not intended to limit the scope of the invention to thispreferred embodiment, but rather to enable any person skilled in the artto make and use the invention.

[0022] Referring to FIG. 1, a driveline assembly of the presentinvention is generally shown at 2. The driveline assembly 2 includesfirst and second axle half-shafts 4 (one shown) supported within an axlehousing 6. A rear differential 100 having a differential housing 102 isrotatably mounted within the axle housing 6. An over-running clutchassembly 10 is coupled to the differential housing 102 and one of theaxle half-shafts 4.

[0023] Referring to FIGS. 2-4, the over-running clutch assembly 10 ofthe present invention includes an outer race 12 having a cylindricalinner surface 14 and is rotatable about an axis 16. The outer race 12includes a case end 18 enclosing a first end of the outer race 12. Theclutch assembly 10 also includes an inner race 20 having a cammed outersurface 22 coaxial with the cylindrical inner surface 14 of the outerrace 12. The inner surface 14 of the outer race 12 and the outer surface22 of the inner race 20 define a gap 24 between the inner race 20 andthe outer race 12. The inner race 20 is rotatable about the axis 16. Theouter race 12 includes a flange 26 or other means for mounting theclutch assembly 10 to a differential housing 28. Preferably, the rollers34, the inner race 20 and the outer race 12 are made from steel. Due tothe high hertzian contact stresses experienced by the rollers 34, theinner surface 14 of the outer race 12 and the outer surface 22 of theinner race 20, the inner surface 14 and outer surface 22 are preferablyhardened and ground.

[0024] The outer surface 22 of the inner race 20 includes a plurality oframp surfaces formed at spaced apart locations which define a pluralityof cammed surfaces on the outer surface 22 of the inner race 20. Aplurality of rolling elements 34 are positioned between the outer race12 and the inner race 20 with one roller 34 being located at the centerof each of the cammed surfaces of the inner race. The rolling elements34 have a diameter which is smaller than the gap 24 between the innersurface 14 and the midpoint of the cammed outer surface 22, but greaterthan the gap between the outer portions of the cammed surfaces and theinner surface 14. A retainer 36 interconnects all of the rollingelements 34 and causes the rolling elements 34 to circumferentially movein unison with one another. The retainer 36 is rotatable about the axis16 with limited relative rotation with respect to the inner race 20. Theretainer 36 also includes a retainer tab 38 extending axially toward aninner surface 40 of the case end 18. A distal end 42 of the retainer tab38 is adjacent the inner surface 40 of the case end 18.

[0025] A first biasing element 81 is mounted onto the retainer 36 tomaintain the position of the retainer with respect to the inner racesuch that the rollers are normally held in the middle of the cammedsurfaces. An actuation disk 46 is disposed between the retainer 36 andthe inner surface 40 of the case end 18. The actuation disk 46 has anouter diameter 48 and an inner diameter 50. The actuation disk 46further includes a notch 54 located radially about the outer diameter48. The notch 54 is adapted to engage the retainer tab 38 therebypreventing rotational motion of the actuation disk 46 relative to theretainer 36, while allowing axial motion of the actuation disk 46relative to the retainer 36. A second biasing element 56 is disposedbetween the actuation disk 46 and the inner surface 40 of the case end18 to bias the actuation disk 46 away from the case end 18 and towardthe retainer 36. Preferably, the second biasing element 56 is a wavespring.

[0026] In the preferred embodiment, the first biasing element is acentering spring supported by the retainer 36 and engaging the innerrace 20 to keep the retainer in position to keep the rolling elements 34in the center of the cammed surfaces of the inner race 20 to allow theouter race 12 and the inner race 20 to rotate freely with respect toeach other. The centering spring includes a plurality of small tangs(not shown) extending radially in or out to engage small notches (notshown) on the hub 72 of the inner race 20. The biasing force of thecentering spring must be carefully calibrated for the clutch assembly10. The centering spring must provide enough force to move the retainer36 and rolling elements 34 to the neutral position easily when theclutch assembly 10 is dis-engaged, but not so much force that thefriction between the actuation disk 46 and the case end 18 cannotovercome it to actuate the clutch assembly 10.

[0027] Referring to FIG. 5, the actuation disk 46 may further includegrooves milled into one face to assist the displacement of lubricant,especially at low temperatures when the viscosity can increase to suchlevels that actuation is impaired. These grooves can be radial orcircumferential, or even spiral in both directions to assist the“corkscrewing” of the thickened lubricant out of the interface zone asthe parts rotate relative to each other.

[0028] The clutch assembly 10 includes an actuator 58 to selectivelyovercome the second biasing element 56 to force the actuation disk 46into contact with the case end 18. The actuation disk 46 is free to moveaxially with respect to the retainer 36, so when the attractive force ofthe actuator 58 overcomes the force of the second biasing element 56,the actuation disk 46 will move axially toward the inner surface 40 ofthe case end 18 until the actuation disk 46 contacts the inner surface40 of the case end 18. When the actuation disk 46 is brought intocontact with the inner surface 40 of the case end 18, the relativerotational motion of the outer race 12 and case end 18 with respect tothe actuation disk 46 will frictionally be transferred to the actuationdisk 46. The actuation disk 46 is linked rotationally andcircumferentially to the retainer tabs 38, therefore the rotationalmovement of the outer race 12 and case end 18 will be transferredthrough the actuation disk 46 and to the retainer 36.

[0029] Rotational movement of the retainer 36 with respect to the innerrace 20 moves the rolling elements 34 along the ramped surfaces untilthe rolling elements 34 are no longer in the centers of the cammedsurfaces. Since the gap 24 is not large enough to accommodate thediameter of the rolling elements 34, when the rolling elements 34 moveout of the centers of the cammed surfaces, the rolling elements 34become wedged between the outer surface 22 of the inner race 20 and theinner surface 14 of the outer race 12, thereby locking the inner race 20and outer race 12 together rotationally. The ramped surfaces aredesigned such that when the rolling elements 34 wedge between the innerand outer races 12, 20 an angle is formed between the ramped surfaces ofthe inner race 20 and a line tangent to the inner surface 14 of theouter race 12. In order for the rolling elements 34 to wedge properlybetween the inner surface 14 of the outer race 12 and the outer surface22 of the inner race 20, the angle defined by the ramped surfaces and aline tangent to the inner surface 14 of the outer race 12 is preferablybetween approximately four degrees and approximately ten degrees. Ifthis angle is too small, then the hertzian contact forces will be toohigh, crushing the rolling elements 34 and brinnelling the surfaces ofthe inner and outer races 12, 20. If the angle is too large, the rollingelements 34 will squirt out from between the inner surface 14 of theouter race 12 and the outer surface 22 of the inner race 20. The rampedsurfaces and the interaction of the ramped surfaces with the rollingelements 34 are described in detail in U.S. Pat. Nos. 5,927,456 and5,924,510 which are both assigned to NTN Corporation and are herebyincorporated by reference into this application.

[0030] In the preferred embodiment, the actuator 58 comprises anelectromagnetic coil 60 held within a housing 62 mounted to an exteriorsurface of the stationary axle housing 6. The case end 18 includes aplurality of partially circumferential slots 66 extending through thecase end 18 and spaced radially about the case end 18. When energized,the electromagnetic coil 60 produces a magnetic flux which is focusedaround the slots 66 and concentrated on the actuation disk 46. When themagnetic flux passes through the actuation disk 46, the actuation disk46 is magnetically drawn toward the inner surface 40 of the case end 18.Once the magnetic force of the electromagnetic coil 60 overcomes theforce of the second biasing element 56, the actuation disk 46 will startto move toward the inner surface 40 of the case end 18.

[0031] Preferably, the actuator 58 is an electromagnetic coil 60,however it is to be understood, that the present invention could bepracticed with an actuator 58 of some other type. The actuation disk 46could be moved through hydraulic or pneumatic means as well as throughelectromagnetic means. The present invention allows the actuator 58 tobe mounted directly to the stationary axle housing in a drive lineassembly, thereby allowing the differential to fit within existing axlecarriers to make replacement cost efficient.

[0032] When the actuator 58 is de-energized, the magnetic attraction ofthe actuation disk 46 to the inner surface 40 of the case end 18dissipates. As this attraction dissipates, the force of the secondbiasing element 56 quickly overcomes the dissipating magnetic attractionand forces the actuation disk 46 back away from the inner surface 40 ofthe case end 18, thereby eliminating the frictional transfer of rotationto the actuation disk 46. Without a rotational force to pull theretainer 36 and rollers 34 out of the neutral position, the firstbiasing element 81 will force the retainer 36 back into the neutralposition and the rollers 34 back into the middle of the cammed surfaces,thereby allowing the outer race 12 to rotate freely with respect to theinner race 20, and un-locking the clutch assembly 10.

[0033] In the preferred embodiment, the actuation disk 46 includes anannular step 82 extending around the inner diameter 50 of the actuationdisk 46. The annular step 82 faces the inner surface 40 of the case end18, and provides a recess into which the second biasing element 56 ispiloted and can collapse into when the actuation disk 46 is drawn to theinner surface 40 of the case end 18. Preferably, the second biasingelement 56 is a wave spring that fits within the annular step 82 on theactuation disk 46 and collapses within the annular step 82 when theforce of the electromagnetic coil 60 exceeds the spring force of thewave spring 56.

[0034] Preferably, the housing 62 for the electromagnetic coil 60 ismounted to the stationary axle carrier and is located with respect tothe case end 18 by a bearing 68. The bearing 68 can be a ball, roller orjournal bearing and will allow the electromagnetic coil 60 and thehousing 62 to remain stationary with respect to the axlehousing/carrier. This will allow wiring to the electromagnetic coil 60to be simplified because an electrical connection to a rotating body isnot required. A journal bearing or some other type of bearing could alsobe used. Any means suitable to allow relative rotational movementbetween the housing 62 and the exterior surface of the case end 18 isadequate.

[0035] Referring to FIGS. 5 and 6, in the preferred embodiment, theinner diameter 50 of the actuation disk 46 includes a series of innernotches 70. The inner race 20 includes a hub 72 adjacent the cammedouter surface 22 which includes a step 74 extending radially and axiallyoutward. The step 74 extends axially toward the inner surface 40 of thecase end 18 leaving a space 76 between the step 74 and the inner surface40 of the case end 18. The height of the actuation disk 46 is sized tofit within that space 76 such that the step 74 engages the inner notch70 when the actuation disk 46 is biased toward the retainer 36. Thislocks the actuation disk 46 rotationally to the hub 72 of the inner race20. This is helpful to insure that the actuation disk 46 will notinadvertently rotate and cause the clutch 10 to lock up by mistake. Thiscan happen when the viscosity of the oil within the clutch 10 and therotational speed of the outer race 12 combine to frictionally rotate theactuation disk 46 without the actuator 58 attracting the actuation disk46 to the inner surface 40 of the case end 18. As long as the innernotch 70 within the actuation disk 46 is engaged with the step 74 on thehub 72, the actuation disk 46 cannot rotate, and the clutch 10 cannot beinadvertently locked up.

[0036] When the electromagnetic coil 60 is actuated and draws theactuation disk 46 toward the case end 18, the notches 70 on the innerdiameter of the actuation disk 46 will clear the step 74 just beforecoming into contact with the inner surface 40 of the case end 18,thereby allowing the actuation disk 46 to rotate freely within the space76 between the step 74 and the inner surface 40 of the case end 18 andallowing the clutch 10 to lock up. Preferably, the step 74 is formed onthe hub 72 of the inner race 20, however, it is to be understood thatthe step 74 could be formed on a ring 78 that is press fit onto the hub72 of the inner race 20.

[0037] In the preferred embodiment, the retainer tabs 38 extend directlyfrom the retainer 36, however, alternatively, the clutch assembly 10could include an actuation spider 80 mounted to the retainer 36 as shownin FIGS. 4 and 5. The actuation spider 80 is rotationally locked to theretainer 36 such that the actuation spider 80 and the retainer 36functionally act as one component. The first biasing element 81 actsagainst the retainer 36, holding the retainer in position with respectto the inner race 20. The retainer tabs 38 extend from the actuationspider 80 to engage the notches 54 within the outer diameter 48 of theactuation disk 46.

[0038] Referring to FIGS. 1, 7 and 8, the differential housing 102includes an input ring gear 103 mounted to an outer diameter 104 of thehousing 102. Rotational motion from the drive train of the vehicle istransferred to the differential housing 102 through this ring gear. Afirst side gear 106 and a second side gear 108 are mounted within thedifferential housing 102 and are attached to first and second axlehalf-shafts 4 (one shown) of the vehicle. Two or more spider gears 110are mounted in the differential housing 102 so that they match with thefirst and second side gears 106, 108.

[0039] During normal straight line operation, the power provided istransmitted through the ring gear to the differential housing 102.Because there is no relative rotational speed differences between thetwo axles during normal straight line operation, the differentialhousing 102 and axles rotate at the same speed, and there is no relativemotion between the side gears 106, 108 and the spider gears 110. Whenthe vehicle turns, rotational speed differences between the two axlesare caused by the differently sized circles being described by the tireson each side of the vehicle. As the axles turn at different speeds, sidegears 106, 108 also turn at different speeds, but the spider gears 110keep the two axles meshed together and torque is split proportionallybetween the two sides.

[0040] The clutch assembly 10 is mounted within the differential housing102 to allow both the axles of the vehicle to be locked together bylocking the first side gear 106 rotationally to the differential housing102. Referring to FIG. 8, the second side gear 108 is rotatably mountedwithin the differential housing 102 at a second end 114. The second sidegear 108 is fixed axially, but is allowed to rotate independently of thedifferential housing 102. The outer race/case end of the roller clutch10 is fixedly mounted to the differential housing 102 at a first end112.

[0041] As shown in the figures, the clutch assembly 10 and thedifferential housing 102 can each include a flange 116, 118 to allowthem to be attached to one another with mechanical fasteners. However,it is to be understood, that an outer diameter 120 of the outer race 12of the clutch assembly 10 and an inner diameter 122 of the first end 112of the differential housing 102 can be formed with splines therein andsized such that the clutch assembly 10 can be press fit within the innerdiameter 122 of the first end 112 of the differential housing 102 toeliminate the need for mechanical fasteners.

[0042] The first side gear 106 is fixedly mounted to the inner race 20of the clutch assembly 10. In the preferred embodiment, the inner race20 includes a center bore 124 and the first side gear 106 includes anouter diameter 126, wherein the center bore 124 of the inner race 20 andthe outer diameter 126 of the first side gear 106 are adapted to bepress fit or splined together. The center bore 124 of the inner race 20and the center bore of the first side gear 106 may also have splinesformed on them to connect each to a common spline on the first axle/halfshaft, to prevent any relative rotational movement between the innerrace 20 and the first side gear 106. In all of these embodiments, thefirst side gear 106 and the inner race 20 are locked together andfunctionally act as one component.

[0043] The spider gears 110 are mounted within the housing 102 androtate about a first axis 128 defined by a shaft 129 mounted therein.The first and second side gears 106, 108 are mounted to the differentialhousing and rotate about a second axis 130 defined by the first andsecond axle half-shafts which is perpendicular to the first axis. Thespider gears are mounted within the housing and on the shaft and areengaged with both the first and second side gears 106, 108.

[0044] When the clutch assembly 10 is dis-engaged, the inner race 20 andthe outer race 12 are free to rotate relative to each other so the firstside gear 106 and the first axle half shaft 109 are free to rotaterelative to the differential housing 102. If the rotational speed of theaxle half-shafts are different, such as when the vehicle turns, the sidegears 106, 108 also turn at different speeds, but the spider gears 110keep the two axles meshed together and torque is split appropriatelybetween the two sides. In conditions of poor traction (wet roads, snow,ice), one wheel can slip and the differential 100 doesn't allow theother wheel to carry any torque. Under these conditions, a vehicle canhave trouble getting up even a low grade hill.

[0045] When the clutch assembly 10 is engaged, the first axlehalf-shaft, the first side gear 106, the inner race 20, the outer race12 and the differential housing 102 are all locked together so that norelative rotation is allowed. When the first side gear 106 is lockedrotationally to the differential housing 102, the spider gears 110,which are meshed with the first side gear 106 are prevented fromrotating around the first axis 128, and the second side gear 108, whichis meshed with the spider gears 110, is prevented from rotationalmovement relative to the differential housing 102. To simplify, when theclutch assembly 10 is engaged, the two side gears 106, 108, andconsequently the two axle half-shafts are effectively locked together sothat torque is transferred to both axle half-shafts equally and norelative rotation between the two axle half-shafts is allowed.

[0046] The foregoing discussion discloses and describes one preferredembodiment of the invention. One skilled in the art will readilyrecognize from such discussion, and from the accompanying drawings andclaims, that changes and modifications can be made to the inventionwithout departing from the true spirit and fair scope of the inventionas defined in the following claims. The invention has been described inan illustrative manner, and it is to be understood that the terminologywhich has been used is intended to be in the nature of words ofdescription rather than of limitation.

1. A driveline assembly comprising: a first axle half-shaft and a secondaxle half-shaft; an axle housing; a differential housing rotatablymounted within said axle housing; a least two spider gears rotatableabout a first axis and mounted to said differential case for rotationtherewith; a first side gear being fixedly coupled to said first axlehalf-shaft, and a second side gear being fixedly coupled to said secondaxle half-shaft; an clutch assembly coupled to said differential housingand one of said axle half-shafts, said clutch assembly including anouter race having a cylindrical inner surface and being rotatable abouta second axis and a case end enclosing a first end of said outer race,an inner race having a cammed outer surface coaxial with saidcylindrical inner surface and defining a gap therebetween, said innerrace being rotatable about said second axis allowing rotational movementrelative to said outer race, a plurality of ramped surfaces formed atspaced apart locations on said cammed outer surface, said rampedsurfaces defining a plurality of cammed surfaces on said outer surface,a plurality of rollers positioned between said outer race and said innerrace with one of said rollers being located at a midpoint of each ofsaid cammed surfaces, said rollers having a diameter less than said gapbetween said cylindrical inner surface and said midpoints of said cammedsurfaces, a retainer interconnecting all of said rollers and causingsaid rollers to circumferentially move in unison with one another, saidretainer being rotatable about said axis with limited relative rotationwith respect to said inner race, a first biasing element supportedbetween said inner race and said retainer to bias said retainer withrespect to said inner race such that each of said rollers is biased toeach of said midpoints of each of said cammed surfaces, wherein rotationof said retainer with respect to said inner race moves said rollersalong said ramp surfaces to a position where said rollers engage andwedge between said inner and outer races to prevent relative rotationbetween said inner and outer races, thereby locking both of said axlehalf-shafts together rotationally and transferring torque through saiddifferential housing to both of said axles half-shafts.
 2. The drivelineassembly of claim 1, wherein said clutch assembly further includes: aretainer tab extending axially from said retainer toward an axial innersurface of said case end, a distal end of said retainer tab beingadjacent said axial inner surface of said case end, an actuation diskhaving an outer diameter, an inner diameter and a thickness, disposedbetween said retainer and said inner surface of said case end includinga notch located radially about said outer diameter of said actuationdisk, said notch adapted to engage said retainer tab thereby preventingrotational motion of said actuation disk relative to said retainer andallowing axial motion of said actuation disk relative to said retainer,a second biasing element disposed between said actuation disk and saidinner surface of said case end to bias said actuation disk away fromsaid case end and toward said retainer, and; an actuator to selectivelyovercome said second biasing element to force said actuation disk intocontact with said case end, wherein rotation of said outer race and caseend with respect to said inner race is frictionally transferred to saidactuation disk and said retainer, thereby moving said rollers along saidramp surfaces to a position where said rollers engage and wedge betweensaid inner and outer races to prevent relative rotation between saidinner and outer races.
 3. The driveline assembly of claim 2, whereinsaid first axis is established by a shaft mounted within said housing,said spider gears being rotatably mounted to said shaft.
 4. Thedriveline assembly of claim 3, wherein said first side gear is fixedlyconnected to said inner race, thereby fixedly connecting said first axlehalf-shaft to said inner race, and said second side gear is rotatablysupported by said housing, thereby rotatably supporting said second axlehalf-shaft with said housing.
 5. The driveline assembly of claim 3,wherein said inner race is fixedly connected to said first axlehalf-shaft, and said second side gear is rotatably supported by saidhousing, thereby rotatably supporting said second axle half-shaft withsaid housing.
 6. The driveline assembly of claim 3, wherein saidactuator comprises an electromagnetic coil held within a housing mountedto an interior surface of said axle housing and is located with respectto said case end by a bearing therebetween, said case end includingslots spaced radially about said case end, wherein a magnetic flux isfocused around said slots to said actuation disk when saidelectromagnetic coil is energized, thereby magnetically attracting saidactuation disk toward said inner surface of said case end.
 7. Thedriveline assembly of claim 6 wherein said housing for saidelectromagnetic coil is supported on said case end by a bearing to allowsaid case end and outer race to rotate independently of said housing. 8.The driveline assembly of claim 3 wherein said inner diameter of saidactuation disk includes at least one inner notch formed therein and saidinner race includes a hub adjacent said cammed outer surface, said hubincluding at least one step extending radially outward, said stepextending axially toward said inner surface of said case end with a gaptherebetween, said thickness of said actuation disk being sized to fitwithin said gap such that said step engages said inner notch when saidactuation disk is biased toward said retainer to prevent rotation ofsaid actuation disk relative to said hub and inner race, and said innernotch clears said step when said actuation disk is forced into contactwith said inner surface of said case end allowing said actuation disk torotate relative to said hub and inner race.
 9. The driveline assembly ofclaim 8 wherein said step is formed on a collar, said collar having aninner diameter and said hub having an outer diameter, said innerdiameter and said outer diameter sized to allow said collar to be forcedonto said outer diameter of said hub and held thereto by a press fitcondition.
 10. The driveline assembly of claim 3 wherein said firstbiasing element is a centering spring held in place between said innerrace and said retainer to bias said retainer into a neutral positionwherein said rollers are held at said midpoints of said cammed surfaces.11. The driveline assembly of claim 3 wherein said actuation diskfurther includes a recess formed on an axial face of said actuation diskand said second biasing element is a wave spring resting within saidrecess, said recess providing a cavity into which said wave springcompresses when said actuation disk is forced into contact with saidinner surface of said case end.
 12. The driveline assembly of claim 11wherein said actuation disk further includes grooves formed therein toassist in displacement of lubricant.